1. Field of the Invention
The present invention relates to an ultrasonic motor which frictionally drives a moving body with the vibration of a vibrating body, and an electronic device using the same, and, particularly, to an ultrasonic motor which drives a moving body with a vibration obtained by combining a longitudinal vibration and a bending vibration caused on a rectangular vibrating body.
2. Description of the Related Art
Recently, with size reduction, functional enhancement and reduction in consumed power of electronic devices, attention has been paid to ultrasonic motors as an actuator to move operational parts, and achievement of the adoption thereof is increasing. Particularly, many linear type ultrasonic motors which can be driven directly are used in electronic devices, such as a precision stage, which need high-accuracy positioning. There is known a typical linear type ultrasonic motor which utilizes a combined vibration of the longitudinal vibration and bending vibration of a rectangular vibrating body. This ultrasonic motor has four electrodes provided at one side of a piezoelectric element to be a vibrating body, which has a rectangular plate shape, and grouped into two sets of electrodes each having two orthogonal electrodes, and a drive signal is applied to one of the two sets of electrodes to provide a vibration necessary to drive the vibrating body (see JP-A-7-184382). The moving direction of the moving body is determined by selecting electrodes to which the drive signal is to be applied. This ultrasonic motor therefore is characterized by simplification of the drive circuit due to a single drive signal used.
However, the ultrasonic motor using the vibration of a rectangular plate is disadvantageous in that the exciting force of the vibration (particularly, bending vibration) caused on the rectangular plate to be the vibrating body is weak, so that the ultrasonic motor has a smaller output and lower efficiency.